Definition of “cool (sb/sth) down/off” - Learner’s Dictionary

cool (sb/sth) down/off

phrasal verb with cool us uk /kuːl/ verb [ I, T ]

B2 to become less hot, or to make someone or something become less hot:

We went for a swim to cool off.

B2 to become calmer, or to make someone become calmer:

Leave her to cool off and then talk to her.

(Definition of “cool (sb/sth) down/off” from the Cambridge Learner's Dictionary © Cambridge University Press)